Field of the Invention
The present invention relates to a zoom lens and an image pickup apparatus including the zoom lens, and more particularly, to a zoom lens suited for use in a broadcasting television camera, a cinema camera, a video camera, a digital still camera, and a silver-halide film camera.
Description of the Related Art
In recent years, a zoom lens having a small size, a light weight, a wide angle of view, a high magnification ratio, and high optical performance is desired for use in an image pickup apparatus, e.g., a television camera, a cinema camera, a photographic camera, or a video camera. In particular, an image pickup device, e.g., a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS), which is used in a television or cinema camera serving as a professional moving image pickup system, has a substantially uniform resolution over the entire image pickup range. Therefore, a zoom lens using the image pickup device is required to have a substantially uniform resolution from the center to the periphery of the screen. There are also needs for reductions in size and weight for an image pickup mode that places emphasis on mobility and operability.
Meanwhile, when a wide angle lens having a short focal length at a wide angle end is used, a wide range may be photographed, and perspective may be enhanced. Among users who want to utilize the photographing effect, there is an increased demand for a wide angle zoom lens having a wider angle, a high magnification ratio, a small size, a light weight, and high performance.
As a wide angle zoom lens, there is known a negative lead type zoom lens including a total of four or more lens units, of which a lens unit having a negative refractive power is arranged closest to an object side.
For example, in Japanese Patent Application Laid-Open No. 2014-38153, there is disclosed a six-unit zoom lens having an F-number of from about 2.2 to about 2.5 at a wide angle end, an angle of view of from about 45 degrees to about 65 degrees at the wide angle end, and a magnification ratio of from about 1.4× to about 1.7×. Moreover, in Japanese Patent No. 4957124, there is disclosed a six-unit zoom lens having an F-number of from about 1.8 to about 2.5 at a wide angle end, an angle of view of from about 35 degrees to about 60 degrees at the wide angle end, and a magnification ratio of from about 1.2× to about 1.5×. Each zoom lens includes, in order from an object side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a negative refractive power, a fifth lens unit having a positive refractive power, and a sixth lens unit having a positive refractive power.
However, in the zoom lens disclosed in each of Japanese Patent Application Laid-Open No. 2014-38153 and Japanese Patent No. 4957124, the refractive power and the lens configuration of each lens unit are disadvantageous for achieving a wider angle and a higher magnification, with the result that it becomes difficult to suppress an increase in lens diameter accompanying the achievement of the wide angle and an increase in total length accompanying the achievement of the high magnification. In particular, when the angle of view exceeds 70 degrees at the wide angle end, a tendency toward the increased lens diameter becomes significant, and when the magnification ratio exceeds 2×, a tendency toward an increase in movement amount of a magnification varying lens unit becomes significant.